In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.
For example, for future generations of mobile communications systems frequency bands at many different carrier frequencies could be needed. For example, low such frequency bands could be needed to achieve sufficient network coverage for wireless radio transceiver devices and higher frequency bands (e.g. at millimeter wavelengths (mmW), i.e. near and above 30 GHz) could be needed to reach required network capacity. In general terms, at high frequencies the propagation properties of the radio channel are more challenging and beamforming both at the access node of the network and at the wireless radio transceiver devices might be required to reach a sufficient link budget.
The wireless radio transceiver devices could implement beamforming by means of analog beamforming, digital beamforming, or hybrid beamforming. Each implementation has its advantages and disadvantages. A digital beamforming implementation is the most flexible implementation of the three but also the costliest due to the large number of required radio chains and baseband chains. An analog beamforming implementation is the least flexible but cheaper to manufacture due to a reduced number of radio chains and baseband chains compared to the digital beamforming implementation. A hybrid beamforming implementation is a compromise between the analog and the digital beamforming implementations. As the skilled person understands, depending on cost and performance requirements of different wireless radio transceiver devices, different implementations will be needed.
Different antenna architectures for different frequency bands are being discussed for wireless radio transceiver devices. At high frequency bands (e.g. above 15 GHz) something called “panels” are being discussed. These panels may be uniform linear/rectangular arrays (ULAs/URAs), for example steered by using analog phase shifters. In order to get coverage from different directions, multiple panels can be mounted on different sides of the wireless radio transceiver devices.
Even though wireless radio transceiver devices may be stationary, and experience a fairly stationary radio propagation channel it might be challenging for a wireless radio transceiver device applying analog or hybrid beamforming to find the optimal (or close to optimal) phase settings per antenna element in order to maximize some metrics (for example user throughput) due to lack of sufficient channel state information and too many possible phase settings.
Hence, there is still a need for improved channel condition estimation.